After MD12, Barcelona was 9 points ahead of Madrid (w/extra game played) and 10 points ahead of Atlético (equal GP).
Fast forward going into the Christmas break, and now Atleti is three points ahead and Madrid is two points ahead (both with games in hand). Barcelona have only picked up 5/21 points in their last seven games while Atleti is 18/18 and Madrid is 16/21 in that same time. For the white club, this is just them starting to get themselves straightened out a bit from a rough first two months of the season. For Los Rojiblancos, they are clearly a contender for La Liga this season. I remember in 2020-'21 when they won the league that they rescued a lot of points from 90+ minute winning goals, and they're doing that again now. They're probably the deepest of the three teams as well, which only helps give them staying power.